Rack and pinion assembly

ABSTRACT

A rack and pinion assembly, especially suited for automotive steering linkages, having at least one yoke member slidably supporting the rack bar on the side remote from the rack, and preferably directly opposite that portion of the rack engaging the pinion, wherein the yoke is urged against the rack bar by a spring biased slipper in wedge-fitting, sliding relationship with the yoke. The slipper and yoke have inclined mating surfaces which establish a nonreversing wedge angle relationship so that the spring bias need only be sufficient to take up looseness and wear without supporting the load on the yoke.

United States Patent Frederick J. Adams Campton, England 882,065

Dec. 4, 1969 June 22, 197 l 1 Cam Gears Limited Hltchln, Englandlnventor Appl. No. Filed Patented Assignee RACK AND PINION ASSEMBLY 1 1Claims, 5 Drawlng Figs.

UNlTED STATES PATENTS 8/1939 Keitel 4/ 1959 Davidson 74/422, 74/29 Fl6h1/04, Fl6h 19/04 74/29, 422, 388 PS Primary Examiner-William F. O'DeaAssistant Examiner-Wesley S'. Ratliff, Jr. Attorney-Hill, Sherman,Meroni, Gross and Simpson ABSTRACT: A rack and pinion assembly,especially suited for automotive steering linkages, having at least oneyoke member slidably supporting the rack bar on the side remote from therack, and preferably directly opposite that portion of the rack engagingthe pinion, wherein the yoke is urged against the rack bar by a springbiased slipper in wedge-fitting, sliding relationship with the yoke. Theslipper and yoke have inclined mating surfaces which establish anonreversing wedge angle relationship so that the spring bias need onlybe sufficient to take up looseness and wear without supporting the loadon the yoke.

BACK AND PINION ASSEMBLY BACKGROUND OF THE INVENTION 1 Field of theInvention This invention relates to the art of rack and pinionassemblies for automotive steering linkages and the like, andspecifically deals 'with the supporting of rack bars in assemblies toeliminate lost motion and automatically compensate for wear.

2. Description of the Prior Art Supporting yolks or saddles for the rackbars of rack and pinion assemblies have been resiliently urged againstthe rack bar by springs, as in U.S. Pat. No. 3,347,l09 dated Oct. I7,1967, or by rubber blocks, as in British Pat. No. 892,683 published Mar.28-, 1962. Such resilient supports must be adequate enough to maintainthe yoke or saddle in good bearing engagement with the rack bar and tomaintain the rack in proper meshed condition with the pinion. Shimadjustments or adjusting screws have been required in such installationsto properly load the wear takeup means so that variations in tolerancesof the components might be accommodated.

SUMMARY OF THE INVENTION The present invention now provides a wedgesupport for the yokes or bearing saddles of rack and pinion assemblies.This wedge support is spring-biased to compensate for wear between theyoke and rack bar, but the spring load does not carry the bearing loadbecause the wedge angle is such that the wedge support will remain inposition even when loaded by a large force. The supporting wedge, evenwhen loaded with a very light spring, will not slip backward underbearing loads imposed on it by the yoke or saddle which it supports.

The degree of irreversibility of the wedge is thus controlled by theangle of wedge slope and by the strength of the biasing spring. Thebiasing spring is primarily a wear takeup means and not a support means.

The yokes or saddles are preferably molded plastics material such asnylon, Teflon" (polytetrafluoroethylene,) and the like. The wedge memberor slipper coacting with the yoke or saddle may also be composed of thesame plastics material. It should be understood, however, that eitherthe yoke or the slipper, or both, can be metal, such as steel.

A feature of the invention includes the provision of a resilient cushionbetween the yoke member, its housing, or the slipper, so that undershock conditions the yoke and slipper can move slightly in a directionaway from the pinion without causing the slipper to back off the yoke.The resilient cushion material may be rubber or a plastics material suchas Microvon (a trademark of Rubber Plastics Ltd. for a micro cellularpolyurethane rubber.)

It is then an object of this invention to provide a rack and pinionassembly with a rack bar supporting yoke carried on a wedge which willmaintain the yoke in good bearing engagement with the rack bar and willmaintain the rack in meshed engagement with the pinion.

Another object of this invention is to provide a springbiased wedgeslipper support for the yoke or saddle of the rack bar in a rack andpinion assembly.

Another object of this invention is to provide a bearing support for arack bar of a rack and pinion assembly which will accommodate widetolerance variations, will take up all looseness in the components, andwill automatically compensate for wear while solidly supported on aspring-biased wedge slipper that will not back off under heavy loads.

Another object of the invention is to provide spring-biased wedge takeupfor the supporting yokes of rack bars in rack and pinion assemblies onlyrequires a slight spring bias to take up wear and to prevent movement ofthe wedge out of tight fitting engagement with the yoke.

A still further object of this invention is to provide some resiliencein a wedge supported bearing for the rack bar of a rack and pinionassembly.

Another object of the invention is to provide a wedge support for thebearing yoke of the rack bar in a rack and pinion assembly which has anirreversible wedge angle relationship with the yoke.

Other and further objects of this invention will be apparent to thoseskilled in this art from the following detailed description of theannexed sheet of drawings which, by way of preferred examples only,illustrates several embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view takentransversely to the longitudinal axis of the rack bar of a rack andpinion assembly according to this invention;

FIG. 2 is a cross-sectional view taken generally along the line II-II ofFIG. 1 and showing the yoke and wedge slipper in bottom plan view;

FIG. 3 is a fragmentary view similar to FIG. 1, but illustrating amodified form of the invention;

FIG. 4 is a fragmentary cross-sectional view of a still further modifiedform of the invention;

FIG. 5 is a pair of diagrammatic views illustrating the wedge action ofthe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS. 1 and 2, apart cylindrical rack bar 1 has a rack 2 engaging a pinion 3 so thataxial rotation of the pinion will drive the rack bar longitudinally overthe pinion. A yoke or saddle member 4 has a part cylindrical recess 5complementary to and seated on the cylindrical surface of the rack bar 1at a position directly opposite the position at which the rack 2 engagesthe pinion 3. The yoke member 4 is cylindrical and has its cylindricalsurface 4a extending in a plane normal to the plane of the rack 2 whenthe yoke member is seated on the rack bar, and this plane intersects thelongitudinal axis of the rack bar 1.

The yoke member 4 is slidably mounted in the cylindrical bore of ahousing 6 for the rack and pinion assembly. An end plate 7 closes theend of the cylindrical chamber portion of the housing 6. As shown, thehousing rotatively mounts the pinion is ball bearings, and the pinionshaft projects through the housing.

The yoke 4 on the end thereof remote from the bearing recess 5 has achannel 8 extending diametrically thereacross with an inclined floor orbottom 9. The surface of the floor 9 is in a plane inclined relative tothe plane of the rack 2.

A slipper member 10 is slidably mounted in the channel 8 between thefloor 9 and the end plate 7 and this slipper member has an inclinedsurface 11 mating with the floor 9.

A coil spring 12 bottomed at one end against the housing 6 has its otherend received in a recess 13 of the slipper 10. This spring 12 biases theslipper l0 upwardly on the inclined floor 9 of the yoke member 4.

It will be apparent from FIG. 1 that the slipper member 10 and the yolkmember 4 are in wedge relationship, with the inclined surfaces 9 and 11sliding over each other, thereby causing the yoke to be biased in adirection urging the rack 2 and pinion 3 in meshed engagement. Since theslipper I0 is constantly spring biased towards the rack and pinion intoengagement, the arrangement eliminates all mechanical lost motionbetween the components and automatically compensates for wear betweenthe components. The degree of irreversibility of the slipper 10 iscontrolled by the angle of slope of the engaging inclined surfaces 9 and11 relative to the plane, which includes the rack 2, by the strength ofthe spring.

The angle of inclination of the mating surfaces 9 and 11 is such as tomultiply the applied force of the spring 12 and to change the directionin which it acts.

In the diagrams of FIG. 5 the force F represents the springapplied biasl2, and Q is the larger force to be exerted on the yoke member 4.Disregarding friction, the forces must act normal to their surfaces sothat the actual force on the inclined surface is not 0, but a largerforce F,,. Summing up the forces in the horizontal and verticaldirections shows that:

ceeded by the friction between the face of the wedge and the 10 adjacentbody on which it rests, and the wedge will remain in position even whenloaded by the large force 0.

The wedge angle relationship of the slipper and yoke is such as tomaintain a small angle 0, and the load impose on the yoke 4 by the rackbar ll will not slide the slipper It) even though the load is materiallygreater than the spring bias. The wedge angle relationship may varydepending on the coefficient of friction between the floor 9 and theinclined surface Ill of the slipper. In general, an angle of inclination(angle 6) of from l20 is especially useful.

In the embodiment of FIG. 1 the coacting yoke d, slipper w, and endplate 7 form a relatively rigid stack supporting the rack bar I.

In the modification shown in FIG. 3, parts identical with partsdescribed in FIGS. I and 2 have been marked by the same referencenumeral. However, as shown in FIG. 3, the end plate 7 of the FIG. Iembodiment is replaced with a disc 14 retained in the housing 6 by anannular spring clip I5 seated in a complementary recess in thecylindrical bore of the housing which slidably mounts the yoke 4. Theslipper may be made of mild steel, and a lubrication port I6 is providedin the housing communicating with the engaging inclined surfaces 9 andII. An O-ring seal 17 is provided in a groove around the yoke tto seallubricant in the cylindrical chamber portion of the housing whichreceives the slipper member.

A plunger (not shown) can be inserted through the port 16 duringassembly to urge the slipper member MD to the right, as shown in FIG 3,thereby releasing pressure from the yoke 4 to allow the yoke to moveaway from the rack bar I and permit easy assembly of the rack andpinion.

The slipper 10 may be seated directly against the closure disc M, as inthe FIG. I embodiment, or, as illustrated in FIG. 3, a resilient ring I8may be interposed between the disc I4 and a second disc I9 overlying theslipper l0 and slidable in the housing 6. This ring I8 not only acts asa seal for lubricant in the housing, but also provides a cushioning forthe yoke 4 and slipper 110 against chock forces.

In the embodiment of FIG. 4, parts identical with parts described inFIGS. I and 2 have also been marked with the same reference numerals. InFIG. 45, however, the cushioning against the shock forces isaccomplished without the use of the auxiliary disc 19. In FIG. 43 a disc20 of cushion material is in terposed between the closure plate 7 andthe slipper 10. This resilient disc 20 is preferably made of a plasticsuch as Microvon, and not only cushions the slipper against the shockforces, but eliminates rattling of the assembly.

From the above-descriptions it will, therefore, be understood that thisinvention now provides wedge-type takeup and wear compensating means forrack and pinion assemblies.

I claim as my invention:

1. A rack and pinion assembly having a housing rotatably mounting apinion and receiving a rack bar therethrough with a rack in meshedengagement with the pinion, a yoke slidably mounted in the housing onthe side of the rack bar remote from the rack and slidably supportingthe rack bar, said yoke member having an abutment surface inclinedrelative to the plane of the rack and on the end thereof remote from therack bar, a wedge-shaped slipper member in said housing having anabutment surface mating with the inclined surface of the yoke, meansclosing the housing confining the slipper member against the yoke, andspring means biasing said slipper member up the inclined surface of theyoke to hold the yoke against the rack bar and the rack in meshedengagement with the pinion.

2. In a rack and pinion assembly including a housing rotatably mountinga pinion and receiving a rack bar therethrough with a rack in meshedengagement with the pinion and a yoke slidably mounted in the housinghaving a recess slidably supporting the rack bar on the side thereofremote from the pinion, the improvement of a wedge member slidable inthe housing in wedge relationship with the yoke for urging the yokeagainst the rack bar, and spring means biasing said wedge to take uplooseness and compensate for wear of the yoke and parts supportedthereby.

3. The rack and pinion assembly of claim I where the angle ofinclination of the mating wedge surfaces is from l0-20 and the springbias load is less than the load supported by the wedge slipper.

43. The assembly of claim I wherein the slipper member has a channelreceiving the spring.

5. The assembly of claim I wherein' the slipper member is composed of aplastics material.

6. The assembly of claim I. wherein the slipper member is bottomed on aresilient cushion to accommodate slight movement of the yoke under shockloads imposed on the rack and pinion.

7. The assembly of claim I wherein a resilient cushion is interposedbetween the closed end of the housing and the slipper member capable ofabsorbing shock loads.

The assembly of claim I wherein the housing has a port accommodatinginsertion of a probe to release the wedge.

9. The assembly of claim I wherein the housing space between the yokeand closed end is sealed to retain lubricant.

10. The assembly of claim 2 wherein the wedge is a slipper having a flatbottom and a wedge surface inclined at a wedge angle relative to saidbottom.

Ill. The assembly of claim 2 wherein the wedge locks the yoke memberagainst movement away from the rack bar.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 585,875 Dated June 22, 1971 Inventor (5) Frederick John Adams It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

line 9, after "in" insert --rack and pinion--;

Column 1,

Column 1, line 12, cancel "yolks" and insert --yokes-; Column 1, line49, after "of insert -of--;

Column 1, line 68, after "provide" insert --a--; Column 1, line 70,after "assemblies" insert --which--;

Column 2, line 57, cancel "yolk" and insert --yoke-; Column 3, line 14,cancel "impose" and insert --imposed-; Column 3, line 48, cancel "chocand insert --shock--.

Signed and sealed this 8th day of February 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

1. A rack and pinion assembly having a housing rotatably mounting apinion and receiving a rack bar therethrough with a rack in meshedengagement with the pinion, a yoke slidably mounted in the housing onthe side of the rack bar remote from the rack and slidably supportingthe rack bar, said yoke member having an abutment surface inclinedrelative to the plane of the rack and on the end thereof remote from therack bar, a wedgeshaped slipper member in said housing having anabutment surface mating with the inclined surface of the yoke, meansclosing the housing confining the slipper member against the yoke, andspring means biasing said slipper member up the inclined surface of theyoke to hold the yoke against the rack bar and the rack in meshedengagement with the pinion.
 2. In a rack and pinion assembly including ahousing rotatably mounting a pinion and receiving a rack bartherethrough with a rack in meshed engagement with the pinion and a yokeslidably mounted in the housing having a recess slidably supporting therack bar on the side thereof remote from the pinion, the improvement ofa wedge member slidable in the housing in wedge relationship with theyoke for urging the yoke against the rack bar, and spring means biasingsaid wedge to take up looseness and compensate for wear of the yoke andparts supported thereby.
 3. The rack and pinion assembly of claim 1where the angle of inclination of the mating wedge surfaces is from10*-20* and the spring bias load is less than the load supported by thewedge slipper.
 4. The assembly of claim 1 wherein the slipper member hasa channel receiving the spring.
 5. The assembly of claim 1 wherein theslipper member is composed of a plastics material.
 6. The assembly ofclaim 1 wherein the slipper member is bottomed on a resilient cushion toaccommodate slight movement of the yoke under shock loads imposed on therack and pinion.
 7. The assembly of claim 1 wherein a resilient cushionis interposed between the closed end of the housing and the slippermember capable of absorbing shock loads.
 8. The assembly of claim 1wherein the housing has a port accommodating insertion of a probe torelease the wedge.
 9. The assembly of claim 1 wherein the housing spacebetween the yoke and closed end is sealed to retain lubricant.
 10. Theassembly of claim 2 wherein the wedge is a slipper having a flat bottomand a wedge surface inclined at a wedge angle relative to said bottom.11. The assembly of claim 2 wherein the wedge locks the yoke memberagainst movement away from the rack bar.